Well, if synthesis cannot be found in publications, and you do not have access to the Synthia program, then you have to develop your own synthesis method analogously to some other biimidazoline derivatives. Chinese authors probably used a commercial compound (presumably synthesis on demand), but without good knowledge of the Chinese language it will be difficult to find a manufacturer.
Note, my drawing shows only the correct skeleton of your molecule, but the rings of a more hydrogenated derivative, biimidazolidine. But the figure shows quite well how a compound skeleton can be constructed through retrosynthetic analysis.